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Proc Natl Acad Sci U S A. 2017 Oct 10;114(41):10966-10971. doi: 10.1073/pnas.1712489114. Epub 2017 Sep 25.

Molecular architecture of the sheathed polar flagellum in Vibrio alginolyticus.

Author information

1
Department of Pathology and Laboratory Medicine, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030.
2
Department of Microbial Pathogenesis, Microbial Sciences Institute, Yale School of Medicine, New Haven, CT 06536.
3
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
4
Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan g44416a@cc.nagoya-u.ac.jp jun.liu.jl2996@yale.edu.
5
Department of Pathology and Laboratory Medicine, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030; g44416a@cc.nagoya-u.ac.jp jun.liu.jl2996@yale.edu.

Abstract

Vibrio species are Gram-negative rod-shaped bacteria that are ubiquitous and often highly motile in aqueous environments. Vibrio swimming motility is driven by a polar flagellum covered with a membranous sheath, but this sheathed flagellum is not well understood at the molecular level because of limited structural information. Here, we use Vibrio alginolyticus as a model system to study the sheathed flagellum in intact cells by combining cryoelectron tomography (cryo-ET) and subtomogram analysis with a genetic approach. We reveal striking differences between sheathed and unsheathed flagella in V. alginolyticus cells, including a novel ring-like structure at the bottom of the hook that is associated with major remodeling of the outer membrane and sheath formation. Using mutants defective in flagellar motor components, we defined a Vibrio-specific feature (also known as the T ring) as a distinctive periplasmic structure with 13-fold symmetry. The unique architecture of the T ring provides a static platform to recruit the PomA/B complexes, which are required to generate higher torques for rotation of the sheathed flagellum and fast motility of Vibrio cells. Furthermore, the Vibrio flagellar motor exhibits an intrinsic length variation between the inner and the outer membrane bound complexes, suggesting the outer membrane bound complex can shift slightly along the axial rod during flagellar rotation. Together, our detailed analyses of the polar flagella in intact cells provide insights into unique aspects of the sheathed flagellum and the distinct motility of Vibrio species.

KEYWORDS:

electron tomography; flagellum; nanomachine; vibrio

PMID:
28973904
PMCID:
PMC5642721
DOI:
10.1073/pnas.1712489114
[Indexed for MEDLINE]
Free PMC Article

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